Like in Brawl, Sakurai will be providing daily updates on the development progress of Super Smash Bros for Wii U/3DS through Miiverse.

Today’s update Sakurai revealed that there is a new visual effect. A red-black effect will appear when you get hit by a powerful blow. This is a good indicator that you are close to death.
(3DS, Super Smash Bros., Wii U)

Oooo, that makes things look a bit more dramatic. When it comes to a fighting game as unique as Smash, visual flare can add quite a bit of satisfaction to each battle.

I can't wait to see that effect in action when it's happening to someone I've just hit with a Spin Attack or something similarly powerful. If it comes with a half-second delay where the opponent is frozen from the sheer power of the blow before flying off, it'd be extremely satisfying.